[A]n international team of researchers, led by two French astronomers... has just discovered a magnetic field on tau Bootis, a star orbited by a giant planet on a close-in orbit... Up to now, only indirect clues pointed to the presence of magnetic fields on stars hosting giant extra-solar planets. This result opens major prospects, in particular the study of the interaction between the planet and the magnetosphere of its star... [A]lthough indirect effects of magnetic fields have already been detected on stars hosting giant extrasolar planets, no direct measurement had ever been done until now... They detected the magnetic field...